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Full text of "Practical Organic Chemistry"

QUANTITATIVE  ESTIMATION

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centrated sulphuric acid and about 10 grams of anhydrous
potassium sulphate. The object of the latter is to promote
oxidation by raising the boiling-point of the liquid. The flask is
clamped over wire-gauze and the contents boiled briskly until
the liquid, which first darkens in colour, becomes clear and
colourless or faintly yellow. When the decomposition is com-
plete (-i hour), the flask is left to cool and the contents then
diluted with 23 volumes of water. The flask is now attached
to the distilling apparatus shown in Fig. 18. It is furnished
with a double-bored rubber cork, through one hole of which a
bulb adapter is inserted (to re-
tain any alkali which may spirt
upwards), the latter being con-
nected with a condenser. The
end of the condenser just dips
below the surface of 25 c.c. of
a half-normal solution of hydro-
chloric or sulphuric acid, con-
tained in a flask or beaker. A
tap-funnel with a bent leg, con-
taining about 30 grams of
caustic soda in 60 c.c. of water,
is inserted through the second
hole in the cork. A few pieces
of porous earthenware or granu-
lated zinc are introduced into
the flask to prevent bumping.
After the apparatus has been
fitted together the caustic soda                      tlc> l8'

solution  is  run in slowly and

the flask shaken. The liquid is then boiled briskly until
no more ammonia is evolved (-|-f hour). This should
be ascertained by testing a drop of the distillate with red
litmus paper. If the operation is complete, the liquid is
titrated with half-normal 'sodium carbonate solution, using
methyl orange as indicator.

Example.0*5151 gram acetanilide required   17*3  c.c.  N/2
sodium carbonate :

25 - 17-3 = 77-    77XO-OQ7XIOO =  IQ.46 per cent_
0-5151

if
*Y'